In recent years it has been increasingly recognized that the conventional straight-shaft design for hand-held rackets used in the game of tennis and the like, as well as the required techniques for using such rackets, is not optimum for either generation of maximum power or for achievement of maximum accuracy in play because the conventional straight-shafted racket does not easily enable a user to constantly make rapid grip adjustments necessary during the course of play. More importantly, it has been recognized that conventional racket designs and play techniques cause or induce physical injury by failing to recognize and compensate for the physiological limitations associated with the movement of a user's wrist, forearm and elbow. Such physical injury and problems include sprain of the ligaments of the small finger (ulnar) side of the wrist as well as the ligaments of the back of the wrist, both of which may be induced by a racket design that promotes a laid-back wrist position in a conventional stroke or swing, a position which affords little shock absorption to protect the ligaments in question. Further, lateral tennis elbow or elbow tendonitis occasioned by overloading the forearm-wrist extensor muscle is induced by a conventional racket design which promotes a faulty or incorrect stroke wherein the elbow leads the racket head in a forearm stroke or in "punching" backhand strokes. Medial tennis elbow is sometimes experienced which is occasioned by overloading the forearm muscle induced by rolling the forearm over in a stroke attempting to induce and/or neutralize the spin associated with the oncoming ball or by utilizing a consistently late forehand stroke which requires excessive wrist snap. Similarly, overhead or service strokes entailing substantial acceleration of the racket head from the initial or starting position (racket head behind the user's shoulders) tend to induce excessive wrist snap and consequential overloading or overstressing of such wrist muscles. Still further, shoulder tendonitis or irritation of the shoulder rotator cuff is sometimes occasioned by overloading or overstressing such muscles in a stroke wherein the arm is at an angle of 90.degree. or more to the body trunk as in a service stroke, a stroke above shoulder height or a high follow-through stroke. All of such overloading/overstressing of the wrist, forearm, elbow and shoulder inducing the previously mentioned and other types of muscle and tendon strain is magnified when a racket stroke entails a wrist or elbow positioning near the limits of its range of substantially unstressed or comfortable movement.
It is well known that players of the games of tennis, squash, racquetball, paddleball, ping pong and the like constantly make grip changes and adjustments during the course of play in preparation of hitting the oncoming ball depending upon the location, speed and type of spin on the ball as well as the player's position relative to the ball and many other factors. A player's grip may likewise vary because of differences in court surfaces causing the ball to bounce higher, lower, slower or faster. This is particularly true in the game of tennis where the playing surface may consist of soft clay, hard clay, grass, astroturf, wood or other surfaces. One's grip may also vary because of the particular type of stroke being used by the player, for example, a stroke to put topspin or backspin on the ball or to achieve a chopping or slicing action. Whatever the game, it is well acknowledged that the grip of the racket is the foundation of many, if not all, shots particularly with respect to the game of tennis. How one holds the racket will influence the angle of the racket face, where one meets the ball in relationship to one's body position, and what happens at the moment of impact of the ball with the racket.
One problem associated with the conventional straight-shafted racket design is that such a design does not always allow for rapid grip adjustments during the course of play within the unstressed or comfortable range of movement of the wrist, elbow and shoulder as well as within one's comfortable range of grasp of the implement handle. For example, in the game of tennis, three basic hand grips are used, namely, the Continental grip, the Western grip and the Eastern grip, each grip having particular advantages and disadvantages depending upon the type and style of play. The Continental grip is the same for both forehand and backhand shots and is advantageous for hitting balls below waist level. Use of the Continental grip is less desirable when hitting balls above chest level because it is extremely difficult to gain good racket face control and it requires an exceptionally strong wrist and excellent timing. Use of the Continental grip in this situation may induce injury to the wrist.
The Western grip closes the face of the racket and is used for exaggerated topspin and groundstrokes where contact with the ball is made in front of rather than alongside the body. Since the hand is basically under the racket to close the racket face, it is extremely awkward to rotate the wrist sufficiently to open the racket face for low ball shots and, when attemped, may cause injury. Furthermore, many players who use the Western grip for forehand shots keep the same grip for backhand shots, hitting the ball with the same face of the racket. This technique puts extreme tension on the elbow and arm and can cause tennis elbow. An alternative Western backhand stroke is to lay the thumb on the straight-shafted handle so that it is pointing directly up the handle as compared to across and around the handle. In this situation, the player must choose to go "over" or "under" for a grip change which still necessitates a high elbow on the stroke and causes difficulty with hitting low balls.
Use of the Eastern grip, which is often referred to as the "shake hands" grip, calls for a definite change of grip between the forehand and backhand positions. The change of grip between backhand and forehand strokes usually requires an approximately one-eighth (1/8) turn grip adjustment(s) or approximately 45.degree. of rotation on the racket handle.
Variations and combinations of the above-identified grips as well as other known grips are likewise used such as the Australian grip, Semi-Western grip and two-handed grips, all of which grips place a certain amount of stress and/or strain on the wrist, elbow and/or shoulder when attempting to make certain shots because of the awkwardness of the particular grip used or the unavailability of nuances of racket work required. For these reasons, tennis players constantly make grip adjustments not only to accommodate the location, speed and/or spin associated with the oncoming ball but also to reduce the probability of overstressing or overloading the wrist, elbow and/or shoulder. A conventional straight-shafted racket design does not afford easy transition from one grip to another.
Furthermore, in the game of tennis as well as squash, racquetball, paddleball, ping pong and the like, the various types of strokes include backhand, forehand, overhead and serve, all with or without slicing or chopping action. Two basic categories of wrist strokes or a combination thereof are generally used during the course of play, the first category being the snap-wrist stroke and the second category being the locked-wrist stroke. As the name applies, the snap-wrist stroke or swing entails forward motion of the arm in a plane to contact the ball with the racket and simultaneous forward snapping, rolling or acceleration of the wrist about an axis in a plane parallel to the plane of the palm of the hand, the snap or roll occurring through and past the range of comfortable wrist pivoting and through an arc of normally up to about 120.degree. . In the locked-wrist stroke or swing, the wrist is locked and the arm swung in a forward and upward arc while the conventional racket is ideally maintained in a "heads-up" position wherein the racket head is higher than the racket handle, such racket positioning requiring an upward pivoting of the user's hand about an axis of the wrist in a plane perpendicular to the plane of the palm of the hand towards the upper limits of comfortable wrist pivoting in this direction, namely, through an angle of about 40.degree.. Variations or combinations of these basic stroke categories are encountered when topspin, backspin, chop or slicing action is applied to the ball on impact by a stroke entailing extreme pivoting movement of the wrist about the axis perpendicular to the palm of the hand commonly called "laying back of the wrist" and/or by rolling of the forearm about its longitudinal axis. This is true regardless of the particular grip being used. In all of these strokes, the wrist, forearm and elbow are often driven or forced through, or required to assume at least a momentary position beyond the normal, unstressed or comfortable range of movement about their respective pivot axes. Likewise, in all of these strokes, conventional racket designs and playing techniques can induce physical injury not only because they fail to take into account the natural range of normal, unstressed or comfortable movement of the wrist, forearm and elbow, but, more importantly, because use and play of such rackets also promotes and fosters the use of either a strained wrist position to attain the desired racket position in a locked-wrist stroke or the use of a strained wrist initial and final position to obtain the desired racket position in a snap-wrist stroke. In both of these situations, the muscles and ligaments of the wrist, forearm, elbow and even the shoulder are easily overloaded by the force exerted to accomplish the particular stroke, the racket weight and/or its inertia. It is likewise true that such strained wrist positions interfere with comfortable development of maximum power and consistent accuracy.
A number of prior art patents have recognized certain of these problems and shortcomings by suggesting modifications to the conventional straight-shafted racket design. Such modified racket designs are disclosed in U.S. Pat. Nos. 3,545,755; 4,147,348; 4,183,528; 4,360,201; 4,402,508; and 4,478,416. In each of these patents a racket design is disclosed wherein a racket handle or a racket head is offset from its conventional straight-shafted position to enhance power, accuracy or to reduce possible injury to the user such as tennis elbow or the like. However, each of these prior art designs have failed to produce a commercially viable or acceptable alternative to conventional straight-shafted racket designs because such modified designs were either (1) not satisfactorily comfortable or effective for use with all of the various stroke types or positions normally employed in a hand-held racket type game or (2) such modified designs were not convenient or conducive to allowing a user to easily shift from one grip of the racket handle to another to achieve maximum performance, power, accuracy and comfort during the course of play.